Photo-sensitive coated paper plate for photo-lithography



Jan. 22, 1957 F. E. BRINNICK ETAL PHOTO-SENSITIVE COATED PAPER PLATE FORPHOTO-LITHOGRAPHY Filed Oct. 1, 1953 /W/QFA 577.55

5 5 2 HYLWUAV/L/C (OFF/V6 United States Patent PHOTO-SENSITIVE COATEDPAPER PLATE FOR PHOTO-LITI-IOGRAPHY Frederic E. Brinnick, Westbrook,Towers Doggett, Windham, and Raymond L. Oransky, Portland, Maine,assignors to S. D. Warren Company, Boston, Mass., a corporation ofMassachusetts Application October 1, 1953, Serial No. 383,696

Claims. (Cl. 96-75) This application is a continuation-in-part of ourapplication Serial No. 356,887, filed May 22, 1953, now abandoned.

This invention relates to a new photosensitive coated paper productuseful as a photo-lithographic printing plate for use in planographicprinting.

Planographic printing is a form of lithographic printing which usesplates that are substantially plane, having image areas which areneither intaglioed nor raised above the adjacent surface. In use theblank or unimaged areas are kept wet with aqueous lithographic solutionand so are ink-repellent. The imaged areas, being water-repellent, arenot wet by the aqueous solution and so are free to accept ink from theinking-rolls of the printing press, and when so inked can thereafterprint the image in reverse on any ink-receptive surface brought intocontact therewith. In practice the print i first made on a rubber offsetblanket from which it is transferred to paper so that the final print isidentical with the design on the Plate.

U. S. Patents Nos. 2,626,866 and 2,649,373 disclose photo-sensitivecoated paper lithographic printing plates in which paper bearing-aclay-casein coating has applied thereto a diazonium salt correspondingto the following Formula No. 1.

\N-AI-NE X- wherein or the condensate of such a salt with an aldehyde,or a sulfonate formed by the reaction of a sulfite with said diazoniumsalt or its condensate with an aldehyde. A preferred material is theproduct produced by the action of an alkali-metal sulfite such as sodiumsulfite upon the condensation product of a zinc double salt ofdiazotized para-amino-diphenylamine and formaldehyde in equimolecularproportions.

The light-sensitive coated paper product so made can be kept in apackage for at least a year with substantially no deterioration, so thatat the end of that time it can be used for printing by exposure througha negative transparency to actinic-light. The light insolubilizes theexposed'areas which thereupon become receptive to greasy ink; theunexposed areas remain water-soluble and subsequently are washed away.

The coated paper plate made as described is an excellent product and hascome into wide use. Such plates are capable of printing about 2000excellent halftone prints and at least twice as many prints of line-cutsor type. For some purposes, however, plates capable of yielding agreater number of prints are desired.

The present invention is directed to an improvement over the abovedescribed plate by which improvement a photo-sensitive coated paperplate is produced which is capable of making up to 15,000 or moresatisfactory halftone prints.

The accompanying drawing is a diagrammatic crosssectional illustrationof a sheet of paper in accordance with the present invention. In thedrawing 5 is the paper base, 6 is an optional back coating, 4 is anoptional barrier coating, 3 and 2 are base and top hydrophilic coatings,respectively, and 1 is the photo-sensitive coating all of which will bedescribed in detail hereinafter.

The production of a plate capable of making up to 15,000 or moresatisfactory halftone prints is attained by use of the samephotosensitive compounds disclosed in said Patents Nos. 2,626,866 and2,649,373, in combination with a mineral-coated surface of specificcomposition having the ability of coacting with said photosensitivecompound to yield images capable of making many thousands of prints. Theparticular coated surface which coacts with the photo-sensitive compoundcomprises finely divided mineral pigment of a non-hydrous type such astitanium dioxideand being entirely free from clay or hydrous aluminumsilicate, and containing for each 100 parts of said non-hydrous pigmentfrom 20 to parts and preferably from 35 to 50 parts of a water-solublecarboxyalkylhydroxyalkyl cellulose com pound, such, for example, asodium carboxymethylhydroxyethyl cellulose. The particular cellulosederivative used should have a ratio of carboxyalkyl groups tohydroxyalkyl groups of less than 1.0 and preferably of between 0.3 and1.0. The degree of substitution of the anhydroglucose units presentshould be greater than 0.8 The so-called aluminum-resistant varieties:of carboxymethyl-hydroxyethyl cellulose fall in this range and are verysuitable for use under the invention. Products of medium to lowviscosity are preferred in order to make possible coating compositionsof reasonably high solids content. It is possible to use compounds ofhigher viscosity, however, provided repeated applications are made tobuild up the layer of coating to the desired weight.

A coated paper planographic printing plate designed to produce 15,000 ormore prints requires more strength than one designed to produce only 50copies. The strength demanded is not great, however, and is easilyprovided by a paper base made from moderately beaten chemical wood-pulpfiber and weighing about to pounds per ream of 500 sheets 25 x 38 inchesin size. A specific example of a suitable paper base i one weighing 87pounds per ream made from a furnish containing beaten wood-pulp fibersfrom both coniferous and. deciduous trees, a small proportion of clayfiller, rosin-size, alum, and acidified melamine-formaldehydecondensate. The formed web is surface sized with about 2. pounds perream of the evaporation residue of a solution of ammonical casein madeslightly acidic by formaldehyde, dried and calendered.

For a paper plate expected to give really long printing runs it isessential that the fibrous base of the plate shall not become saturatedwith aqueous lithographic solution, with consequent weakening anddistortion of the base. Such aqueous saturation can be prevented byimpregnation of the paper base with a water-proofing agent,

c g,asphalt. Preferably, however, a Water-impervious barrier-coat isinterposed between the fibrous base and the p l anographic printingsurface to prevent saturation and to ensure long printing runs. Whensuch a barriercgat .used substantially no -aqueous liquid reaches thefibrous base and consequentlyit is not essential for the paper base to.have wet-strength properties. Nevertheless, si 1ce some penetration ofaqueous liquid maybe expected through the cut edges of the plate it ipreferable to give the paper base some degree of wet-strength, as,fonexample, by includingurea-formaldehyde er melamine-formaldehydecondensate in the paper-making furnish.

Paper cqated only on one side is liable to exhibit a tepdency to curl.Hence it is preferable in producing seated, .Pau -p am. aphic. pr n ingpat s h h a k or non-printing side of the plate also be coated in orderto otfsertosorne degree the tendency towardsyctuling which the coatingon the printing-side may induce. The actual composition of vthecoatingon the bac-kof the plate is of little importance, but it is desirablethat the coating be. sufliciently water-resistant that if itinadvertently becomes wetted it will not adhere to the plate cylinder ofthe printing press or to other objects with which it may come intocontact. One suitable coating for th e purpose is about 10 pounds perream of 500 ts cut IZS x 38 inches, of the evaporation residue, of Vrnposition in parts by weight shown in following o mula .NQ-

Clay 100 Casein (solvated by ammonia) 18 Dimethylol urea (toinsolubilize the casein) 2 Water to make solids content about 40%.

factory coating for this purpose is one deposited from.

the composition, given in parts by weight, shown in the followingFormula No. 3:

Clay; 50 A latex ofaemulsion polymerized mixture of 3 moles.

of styrene and 2 moles of butadiene 60 A latex of emulsion polymerizedpolystyrene mol. wt.

about. 80,000. 40 Water to make solids content about 40%.

The dry weight of such barrier-coat required per ream of paper will varyconsiderably, depending upon the surface characteristics of the basestock. It is necessary to apply suflicient so that all fibers arecovered. The usual range is from about 4 pounds to about 10 pounds perream. In any case the coating is adequate if when .subjectedfor 2minutes to the Cobb absorption test (see Standard Test No. T441 of theTechnical Association of the Pulp and Paper Industry) it absorbs notover 0.04 gram of water over an area of 78.5 square centimeters or notover 5.1 grams per square meter. Paper with such a degree of resistancemay for our purpose be considered to be substantially impervious towater. I A suitable, weight of coatir 1g is 7 pounds. per eam Ibarriercoat v previously described is oleophilic rather than hydrophilicConsequently it must be completelycovered by the coating which is toprovide the planographic printing surface. Otherwise any portions not socovered will pick up ink and so spoil any matter printed therefrom.Complete coverage of the barriercoat is ensured by the preferredpractice of the invention in which two successive hydrophilic coatingsare appliedoventhe barrier-coat. Other advantages also ensue from use oftwo successive layers of hydrophilic coating. Among'these are thepossibility of using for thefirst. layerof hydrophilic coatingacomposition having stronger adhesion to the aforesaid barrier-coat thanis given by the top coating containing carboxy-alkylhydroxyalkylcellulose. In such a case the cellulosic coating is less liable to crackthan. whenit. is applied directly over the barrier-coat. Moreover thetotal cost of the composite hydrophilic coating tcanbc less than a.coating of equal weight composed of the preferred top coating alone.

The first hydrophilic coating, whentwo coatings. are used, may comprisenonrhydrous finely divided pigment such as blanc fixe ortitaniumdioxide, but. should not contain a hydrous pigment such as clay.The coating may contain a hydrophilic protein adhesive such as casein,soy protein, animal glue, or the like, said adhesive being set-up orinsolubilized by known agents such, for example, as formaldehyde orformaldehyde-containing compounds.

A preferred first hydrophilic coating to be applied over the previouslymentioned barrier-coat :is' about 10-12 pounds per ream of the;evaporationresiduecofthe coating composition, in parts by weight, shownin. 1 following Formula No. .4:

lrecipitated barium sulfate (blanc 'fixe) 100 Casein (solvated byammonia) 20 Dimethylol urea 4 Water to make solids content. about 34%.

While, as has been pointed out, the preferred .practice is to apply insuccession two hydrophilic coatings of. different compositions, theinvention lS'. not limited to such practice. Very satisfactoryresultscan be obtained by application of a single. layer of. hydrophiliccoating composition comprising titanium dioxide, a water-solublecarboxyalkylhydroxyalkyl cellulose compound such as sodiumcarboxymethylhydroxyethyl cellulose, and an agent. to render thedriedocoating waterainsolublebut stillhydrophilic.

The coating composition used to provide the top orsurface.coat'whether-a singleordoublecoating is used, however, must contain awater-soluble carboxymethylhydroxyethyl cellulose compound, or othercarboxyalkylhydroxyalkyl cellulose, in quantity. amounting to from 20-1070 parts, and preferably from to parts, for'each parts of mineralpigment present. The mineral pigment will contain no clay or otherhydrous pigment, but will contain non-hydrous finely divided pigmentarymaterials such as titanium dioxide. Blanc fixe may be used but issomewhat less satisfactory than titanium dioxide in the top coating. Therutile form of titanium dioxide appears to giveslightly better results.than'the anatase. form in respect to greater length of. printing runsgiven. by. the

esulting plate.

The originally water-soluble cellulose adhesive must be renderedwater-insoluble before thecoated sheet can be used as a printing plate.The treatment used toinsolubilize the adhesive should not appreciablyimpair ethehydrophilic properties or" the adhesive, for the..-adhesivemust not become water-repellent or. water-shedding. There are, however,various known treatments for insolubilizing such a hydrophiliccellulosieadhesive Without seriously afiectingthe hydrophilic propertiesthereof. Oneinsolubilizing treatment that is very effective upon sodiumcarboxyalkylhydroxyal-kyl cellulose iscarried' out by in clusion' in thecoating composition" of significant quantities of partiallycondensedamino-resins, such as-water-soluble urea-formaldehyde ormelamine-forma-idehydecondensates, together with sufficient acidicmaterial'to'keep the pH value of the coating composition below 7.Coating containing such amino-resin insolubilizers should be force-driedwith heat in order to promote curing of the resin, and consequentialinsolubilization of the coating, within a reasonable time. Thetemperature and/or time required for curing will vary'depending upon theparticular'amino-resin used. Particularly useful amino resinsaremelamine-formaldehyde resins'preparedby the partial condensation of onemole of melamine with two to three moles of formaldehyde, for in generalsuch condensates are satisfactorily cured merely by the heating requiredto dry the water from the coating. One such satisfactory resin is thecondensate of 1 mole of melamine with 3 moles of formaldehyde. Aquantity of such aminoresin in the range from A to 1 part for each partof cellulose derivative will ordinarily ensure satisfactoryinsolubilization of the latter without sensibly reducing its hydrophilicproperties.

Besides the previously mentioned essential components of the top coatingcomposition, i. e. non-hydrous pigment, sodium carboxyalkylhydroxyalkylcellulose, and insolubilizer for the latter, the aqueous coatingcomposition may contain small quantities of various additives generallyused in aqueous coating compositions. Such additives include anti-foamagents, flexibilizers, wetting agents, eveners, and the like, in eachcategory of which a great number of items are found. For use in thepresent invention, however, care should be exercised to avoid use ofadditives which will impart appreciable oleophilic properties to thedried coated surface.

A typical surface hydrophilic coating is about 5 pounds per ream of theevaporation residue of the coating composition shown in followingFormula No. 5:

Parts dry weight Acid, e. g. HCl to make pH 5.7. Water to make solidscontent about Any of the coating compositions may be applied byconventional coating means, an air-knife coater being very satisfactory.

The paper plate made as hereinbefore described by application of abarrier-coat and two subsequent hydrophilic coats is, after being dried,subjected to a smoothing or calendering operation to render the surfacelevel. The resulting sheet is then ready to have applied thereto a washcoat of sensitizer. While the sensitizer preferred is a sulfonateresulting from the action of a sulfite, e. g. sodium sulfite, upon oneof the groups consisting of (1) the diazonium salts corresponding to theaforesaid Formula No. 1 and (2) the condensates of such a salt with analdehyde, nevertheless surprisingly good results may also be obtained byuse of the unsulfonated diazonium salt or of its condensate withformaldehyde.

By good results is meant not only that the resulting plate had excellentprinting characteristics, but also that the sensitized plates, whenproperly packaged, had good shelf life at ordinary temperatures.Previous coated paper plates, i. e. clay-casein coated paper plates,sensitized with the unsulfonated diazonium compounds or the aldehydecondensates thereof have had practically no shelf life. In other wordsplates so prepared have to be exposed within a few hours aftersensitization or they become spoiled. Now, contrariwise, properlypackaged plates made with the same unsulfonated product, e. g. theformaldehyde condensate of a zinc double salt of diazotizedpara-amino-diphenylamine, applied over the improved base coatingcomprising carboxymethylhydroxyethyl cellulose compound and titaniumdioxide keep very satisfactorily for several months.

Nevertheless, although the unsulfonated compounds may be used with goodresults, it is still preferred to employ the sulfonates produced by theaction of sulfites on the diazonium compounds or their aldehydecondensates 6 previously described, because of the exceptional stabilityof these sulfonate compounds.

The sulfonate sensitizing compounds may easily be applied from aqueoussolution spread on. the surface of the calenderedcarboxyalkylhydroxyalkyl cellulose and titanium dioxide coating, such asthe one deposited from the composition of Formula No. 5, by means of aconventional air-knife coater.

In a typical example an aqueous solution containing 1 /2% of thesulfonate of the condensation product of a zinc double salt ofdiazotized para-amino-diphenylamine with formaldehyde in equimolecularproportions was applied by means of an air-knife to the surface of thepreviously described calendered carboxymethylhydroxyethyl cellulose andtitanium dioxide coated paper, and the so-treated paper was then driedwith heat in conventional fashion. Care was taken not to expose thecoated paper to direct sunlight or other light of equivalent actinicpower; ordinary illumination from incandescent lamps was used. The driedcoated paper was cut to size and made into packages wrapped with opaquepaper wrappers. The packaged plates were still in excellent conditionafter being stored for a period of 12 months.

In a printing test the printing plate coated with the composition ofFormula No. 5 and subsequently treated and sensitized as described wasexposed under a halftone negative transparency to actinic light from acarbon-arc for about 3 minutes. The plate was then removed from underthe negative, wiped over with a cotton swab moistened with oleic acid tointensify the ink-receptiveness of the exposed image, and was thenswabbed with another swab wet with water which removed from theunexposed areas the still soluble sensitizer as well as any oleic acidintensifier overlying those areas. The so-imaged plate was then wet outwith a commercial aqueous lithographic solution containing glycerine andammonium acid phosphate, and the wet-out plate was run in the usual wayon a rotary offset duplicator. The prints made at the start of the runwere distinct and had a clean background, and after 15,000 prints hadbeen made the quality was still good and the background was still clean.

It is significant that the particular cellulose derivative specified, i.e. sodium carboxylalkylhydroxyalkyl cellulose, is the only adhesive sofar found that gives these excellent results with the sulfonateddiazonium compounds described. When sodium carboxymethyl cellulose wassubstituted for the sodium carboxymethylhydroxylethyl cellulose inFormula No. 5 the resulting plate would print only less than 1500 goodcopies. On the other hand, when water soluble hydroxyethyl cellulose wassubstituted for the sodium carboxymethylhydroxyethyl cellulose inFormula No. 5 the sensitized coating of sulfonated diazonium compoundcould not be completely removed. The small amount of light sensitivecoating remaining on the surface of the plate was acted on by light evenunder conditions of subdued lighting as the plate was being used on theprinting press during the printing operation. After only a few hundredcopies had been printed it was noted that the image had begun to fattenand after about a thousand copies the non-image areas or backgroundbegan to show tone or soiling by ink.

It is also significant that if in Formula No. 5, the sodiumcarboxymethylhydroxyethyl cellulose is replaced by an equal weight of amixture of sodium carboxymethyl cellulose and water-soluble hydroxyethylcellulose in the ratios of 0.8 to 1.0, then the results obtained areentirely different than those obtained by use of Formula No. 5 asstated. In fact the results are quite similar to those given whenhydroxyethylcellulose alone is used as adhesive, in that discolorationor soiling of the background soon occurs as the plate is being used onthe printing press. It appears therefore that the carboxyalkyl andhydroxyalkyl groups must both be present in the same molecule in orderto achieve the superior results of the invention.

Ifthere is used a carboxymethylhydroxyethyl cellulose having acarboxymethyl to hydroxyethyl ratio of less than about 0.3unsatisfactory results will be obtained of a nature similar to thosegiven by plain water-soluble hydroxylethyl cellulose; ,i. e., abackground which cannot be completely desensitized. On the other hand,the carboxymethyl to hydroxyethyl ratio is greater than 1. the number ofprints obtainable from the resulting plate will be noticeablydiminished.

We Wish to point .out that the paper base Whether it contains .amaterial to impart wet strength or :1: Esther it has aback side coatingor not and whether it has a frontside barrier coating or not forms nopart of the present invention, the provision of such a paperbase .forplanographic printing plates being well known in the art. We wish topoint out further that the present invention doesnot reside broadly inthe use of the diazo sensitizers disclosed in Patents Nos. 2,628,865 and2,649,373. The present invention. resides in the use of a paperbasewhich is suitable for a ,planographic printing plate and in the useofthe diazo sensitizers referred to in combhiation with an intermediatecoating or layer which consists esentially of an insolublizedcarboxyalizylhydroxylallryl cellulose adhesive and a non-hydrouspigment, it being understood that said intermediate layer may consist ofa single coating of said composition or two or more coatings thereof ora top coating thereof upon an anchoring coating of another composition,which anchoring coating however must be hydrophilic and free of hydrouspigment such as clay.

Examples of diazonium compounds of Formula No. 1 are the following:

The diazo compounds of 4--(N-benzyl-N-ethyl)-aminoaniline,4-(N-2,6-dichloro benzyl)amino-aniline, 4(N- cyclohexyl")-amino-aniline,4 amino-2,5,4-tribromo-diphenylamine, 4amino2',4,6-trichloro-diphenylarnine, 4 amino-Z- [N- 2,5-diethoxy-phenyl -sulian1idol diphenylarnine, 4 amino3,6-dimethoxy-diphenylamine-2-carboxylic acid,1-amino-2,5-di-n-propoXy-4-methyl-diphenylsulfide, N-(2,6-dichlorobenzyl) -3-arnino-carbazol, 4- (N- 2,3,4,6tetrachloro-benzyl)-amino-aniline,4-(N-2,6-dichloro-benzyl-N-ethyl)-amino-2,5-diethoXy-aniline and 4-amino2,5,4 triethoXy-diphenyiether and their aldehyde condensates andthe sulfonates of both.

The prefer-red sensitizer, referred to above is made by the action ofsodium sulfite upon the condensation product of the zinc double chlorideof diazotized para-aminoo'iphenylamine with an equimolecular quantity offormaldehyde. This is applied in a Weight amounting to about 0.35 poundper reamv We claim:

1. A photo-sensitive coated paper product capable of being transformedby actinic light into a planograph printing plate comprising a paperbase having a calendered coating layer thereon, said coating consistingessentially of an insolubilized carboxymethylhydroxyethyl celluloseadhesive in which the ratio of carboxymethyl groups to hydroxyethylgroups is within the range from 0.3 to ,1 and in which the degree ofsubstitution of anhydroglucose n R stands for a member of the groupconsisting of aryl groups and aryl groups substituted by a memberselected from the group consisting of aIKYL-alkQXY and carboxyl groupsand halogens,

R1 stands for a member of the group consisting of hydrogen and alkyl,

N stands for nitrogen,

Ar stands for an aromatic residue selected from the group consisting ofphenylene and phenylene substituted by a member of the group consistingof alkyl, alkoxy, aroxy, arylsulfamido, and halogen, and

X stands for the equivalent of an anion of an acid (2) the condensatesof (l) with aldehydes, ('3) sulfonates obtained by reaction of a sulfiteupon (1), and (4) sulfonates obtained by reaction of a sulfite upon (2).

2. Product according to claim 1 in which the adhesive in the calenderedcoating layer comprises sodium carboxymethylhydroxyethyl cellulose whichhas been insolubilizecl by an amino-resin.

3. Photo-sensitive coated paper product capable of bein'g'transformedinto a planogi-aphic printing plate by actinic light which comprises'apaper base, on one side of said paper base a barrier-coatsubstantiallyimpervious to water, over said barrier-coat an anchoring coat comprisingnon-hydrous pigment and insolubilized protein adhesive, over saidanchoring coat a calendered hydrophilic coating layer consistingessentially of titanium dioxide pigment and insolubilizedcarboxymethylhydroxyethyl cellulose adhesive in which the ratio ofcarboxymethyl groups to hydroxyethyl groups is within the range from 0.3to 1 and in which the degree of substitution of anhydroglucose units isgreater than 0.8, and-over said calendered hydrophilic coating layer aphoto-sensitive layer comprising a sulfonate produced by the action of asulfite upon a member of the group consisting of (1) diazoniurn saltscorresponding to the formula R-stands for a member of the groupconsisting of aryl groups and aryl groups substituted by a memberselected from the group consisting of alkyl, alkoxy and carboxyl groupsand halogens,

R1 stands for a member of the group consisting of hydrogen and alkyl,

Nstands for nitrogen,

Ar stands for an aromatic residue selected from the group consisting ofphenylene and phenylene substituted by a member of the group consistingof alkyl, alkoxy, aroxy, arylsulfamido, and halogen, and

X stands for the equivalent of an anion of an acid,

and (2) the condensates of (l) with aldehydes.

4. Product according totclaim 3 in which the photosensitive diazosulfonate is one obtained by the action of a .sulfite upon aformaldehyde condensate of a paradiazonium salt of a diphenylamine.

.5. Productas defined in claim 3 in which the non-hydrous pigment isblanc fixe.

References Cited in the file of this patent UNITED STATES PATENTS2,474,700 Sliflrin June '28, 19.49

2,570,262 Newman Oct. 9, 1951 2,591,309 Slifkin et al Apr. 1, 19522,626,866 Neugebauer et al Jan. 27, 1953 2,649,373 Neugebauer et al.Aug. 18, 1953 FOREIGN PATENTS 678,599 Great Britain Sept. 3, 1952

1. A PHOTO-SENSITIVE COATED PAPER PRODUCT CAPABLE OF BEING TRANSFORMEDBY ACTINIC LIGHT INTO A PLANOGRAPH PRINTING PLATE COMPRISING A PAPERBASE HAVING A CALENDERED COATING LAYER THEREON, SAID COATING CONSISTINGESSENTIALLY OF AN INSOLUBILIZED CARBOXYMETHYLHYDROXYETHL CELLULOSEADHESIVE IN WHICH THE RATIO OF CARBOXYMETHYL GROUPS TO HYDROXYETHYLGROUPS IS WITHIN THE RANGE FROM 0.3 TO 1 AND IN WHICH THE DEGREE OFSUBSTITUTION OF ANHYROGLUCOSE UNITS IS GREATER THAN 0.8 AND A GREATERQUANTITY OF A NONHYDROUS PIGMENT OF THE GROUP CONSISTING OF BLANC FIXEAND TITANIUM DIOXIDE AND A PHOTO-SENSITIVE LAYER OVER SAID COATING, SAIDLAYER COMPRISING A PHOTO-SENSITIZER TAKEN FROM THE GROUP CONSISTING OF(1) DIAZONIUM SALTS CORRESPONDING TO THE FORMULA